1. Field of the Invention
The present invention relates to an automatic sewing apparatus for hemming and closing a sleeve used in automatically making a tubular sleeve from a sleeve blank by sewing machines.
The apparatus for making a sleeve, such as making the short sleeve of a T-shirt, requires a device for making a folded line by folding an edge of the sleeve blank in an S-form, a sewing machine for hemming the blank along the folded line, a device for folding the hemmed piece in two along a line orthogonal to the hemming line, that is, folding in halves, and another sewing machine for sewing the edges of the folded piece together into a tubular form.
2. Description of the Prior Art
In the sleeve making apparatus including the noted devices, generally hitherto, each device was mutually separated and some steps of the process of making the sleeve with the apparatus is separated according to the devices. That is, one operator hems with a sewing machine, and the hemmed piece is taken out of the sewing machine and manually folded in half by another operator, and the folded piece is fed into another sewing machine by another operator, then the edges of the folded blank are sewn together.
In such a sleeve making process with such separated steps many operators are required and an assembly line is generally formed in order to improve productivity. Even in the assembly line, a waiting time between consecutive steps is likely to occur, and overall job efficiency is, consequently not high. Therefore, product cost is forced to increase, and working space for folding the blank is needed, aside from the space for installing two sewing machines, and a large working space is required on the whole.
Contrary to the manual work, U.S. Pat. No. 4,428,315 discloses a fully automated assembly for a sleeve making apparatus. In this assembly, by raising the pickup head engaged with the center line of the back side of the sleeve blank, the sleeve blank is folded in, two in the vertical plane, and free edges of the folded blank are put on a conveyor to convey the blank along a folding line direction, then the blank is drawn out of the pickup head and folded in halves.
The assembly disclosed in the noted patent is a fully automatic sleeve making apparatus, which saves labor and installation space, improves efficiency, and lowers product cost. In such an automatic sewing apparatus, however, the blank fold apparatus is very complicated, and it is necessary to pick up the entire blank to and fold it in two, and draw out the folded blank while sliding on the pickup head, so that if the blank is, for example, slippery, it is hard to form the fold neatly. And even when it is folded neatly, it is often somewhat when unfolded the blank is drawn out from the pickup head, so that actually a neatly folded blank is not obtained. As a result, it is very difficult to make a tubular sleeve as intended.
Furthermore, the blank for forming a sleeve is roughly divided into two types by the cutting shape. One is a linear edge type which forms an acute angle between the hemming line and the edges to be sewn together next in order to make the blank folded in two after hemming tubular, and the other is a bent edge on an intermediate part of the edges of the blank. In these two types of blanks, it is necessary to turn the edge direction at the beginning of sewing or in the midst of sewing, but such an operation was not taken into consideration in the conventional fully automatic apparatus disclosed in the above noted patent.